A Crossover Study to Evaluate the Relative Bioavailability of Two Formulations of Deuterated Remdesivir Hydrobromide for Oral Suspension in Healthy Chinese Adults

This is a single-center, open-label, randomized, two-sequence, two-period crossover study to assess the relative bioavailability of two formulations. The test product (T) is the 0.2 g/sachet formulation, and the reference product (R) is the 0.1 g/sachet formulation. The formulations are not identical. The study plans to enroll 48 healthy participants, male and female, who will be randomized in a 1:1 ratio to two dosing sequences (T-R and R-T), with 24 participants per sequence. The administered dose per period is 0.2 g for both T and R. Participants in the T-R sequence receive 1 sachet of the test product (T) in Period 1 and 2 sachets of the reference product (R) in Period 2. Participants in the R-T sequence receive 2 sachets of the reference product (R) in Period 1 and 1 sachet of the test product (T) in Period 2.

Inclusion criteria

• Able to read, understand, voluntarily participate, and sign the informed consent form.
• Aged 18 to 50 years (inclusive) at screening, male or female.
• Body weight ≥50 kg for males and ≥45 kg for females, Body Mass Index (BMI) between 18 and 28 kg/m^2^ (inclusive) [BMI = weight (kg) / height^2^ (m^2^)].
• Vital signs, physical examination, laboratory tests, ECG, and chest X-ray (posteroanterior view) are normal or judged as abnormal without clinical significance by the investigator.
• Participants (including male participants) and their spouses/partners must have no pregnancy plan (including sperm/egg donation) from signing the informed consent form until at least 30 days after the last dose, and voluntarily agree to use effective contraceptive methods.
• Able to communicate well with clinical staff and complete the study per protocol requirements.

Exclusion criteria

• Presence of clinically significant diseases within 12 months before screening, including but not limited to digestive, circulatory, respiratory, endocrine, urinary, immune, nervous system disorders, and mental/psychological diseases.
• History of any condition with bleeding risk, such as acute gastritis or gastric/duodenal ulcer.
• Current history of oral ulcers, or acute or chronic infection within 1 week before screening.
• Major illness or major surgery within 3 months before screening, or anticipated major surgery during the study period.
• Blood donation or significant blood loss (>400 mL) within 3 months before screening.
• Allergic constitution (allergic to multiple foods/drugs), or known allergy to the investigational product, its components, or related products.
• Positive test results for Hepatitis B surface antigen (HBsAg), Hepatitis C virus (HCV) antibody, HIV antigen/antibody, or Treponema pallidum antibody (TP-Ab).
• Positive pregnancy test at screening or baseline, or currently breastfeeding.
• Screening 12-lead ECG showing QTcF ≥470 ms for males or QTcF ≥480 ms for females. QTcF = QT/[(60/HR)^0.33], where HR is heart rate.
• Use of prescription or non-prescription drugs (including traditional Chinese medicine and health supplements) within 14 days or 5 half-lives (whichever is longer) before screening.
• Vaccination with live, attenuated live, or any live virus component vaccines within 12 weeks before dosing, or planned during the study period and up to 8 weeks after the last dose.
• Participation in any clinical trial and receiving at least one dose of investigational product within 3 months or 5 half-lives (whichever is longer) before screening.
• Average weekly alcohol consumption exceeding 14 units within 3 months before screening (1 unit = 285 mL beer, 25 mL spirits, or 100 mL wine).
• Average daily smoking >5 cigarettes or equivalent tobacco within 3 months before screening.
• History of drug abuse within 1 year before screening.
• Positive alcohol breath test or positive urine drug abuse screen at baseline.
• Unable to tolerate intravenous catheter blood collection or has a needle/blood phobia.
• Consumption of specific diets (including dragon fruit, mango, grapefruit, and/or xanthine-containing diet, caffeinated foods or beverages), or strenuous exercise, or consumption of any alcoholic products within 48 hours before dosing.
• Unable to comply with standardized meals (e.g., special dietary requirements, refusal to accept standard meals).
• Occurrence of acute illness with clinical significance or use of any medication between screening and baseline.
• Any other condition that, in the investigator's opinion, may affect the participant's ability to provide informed consent or comply with the protocol, or makes the participant unsuitable for the study, or participation may affect the study results or the participant's safety.